Withdrawal Time

Phentermine Withdrawal Time

Some patients experience phentermine withdrawal when they stop taking the weight loss pills. Symptoms of phentermine withdrawal can include fatigue, low mood (depression), trembling, and insomnia, among other reactions.

Most people do NOT experience phentermine withdrawal ( 1 ), but those who do are understandably eager to know how long it lasts.

How Long Does Phentermine Withdrawal Last?

woman hanging calendar on wall
Phentermine withdrawal time varies from patient to patient

Acute phentermine withdrawal lasts anywhere from about 1-4 days, but general stimulant withdrawal symptoms like depression and fatigue can linger for weeks or months after stopping the medication. As with all drugs, exact phentermine withdrawal time varies from person to person.

There is a lack of concrete evidence about phentermine withdrawal time due to the fact that peer-reviewed studies show phentermine withdrawal does NOT occur, even in cases of extended use ( 1 ). However, actual phentermine users, especially those who have taken phentermine for long periods of time or at high doses, often report one or more withdrawal symptoms.

Phentermine withdrawal symptoms like depression, fatigue, and trembling are typical of stimulant withdrawal. While phentermine is NOT an amphetamine, the two substances have very similar chemical structures, so there are some parallels between amphetamine and phentermine withdrawal.

Phentermine Withdrawal Time by the Hour

Stimulant withdrawal symptoms can be broken-down into two main phases: initial crash and protracted withdrawal ( 2 ). The initial crash takes place immediately after the last dose of the stimulant, while protracted withdrawal refers to all of symptoms a user experiences in the weeks to months after their last dose.

12-36 Hours

In the first 12-36 hours after stopping a stimulant, the user experiences a “crash” that leaves him or her craving more. This rapid crash is responsible for the characteristic cravings/relapses associated with stimulant dependence.

Soon after, users may begin to experience psychological symptoms like increased anxiety, depression or inability to feel pleasure (anhedonia). This low feeling is often followed by intense fatigue, sometimes coupled with insomnia.

At this point, it is common for people to fall asleep for an extended period of time, only to be awoken by intense hunger.

1-4 Days

After this initial crash, symptoms of stimulant withdrawal are usually the opposite of reactions caused by the drug.

In the 1-4 days after the last dose, users may feel:

  • Fatigued
  • Mental & physically drained
  • Depressed
  • Disinterested

Weeks to Months Later

Post-acute withdrawal symptoms (PAWS), such as depression/detachment, cravings, and insomnia, may come and go over the next few weeks or months. Depression and feelings of unhappiness may linger for up to 6-18 weeks after the last dose.

The biggest risk during stimulant withdrawal is the intense depression and inability to feel pleasure, which may be accompanied by suicidal ideation ( 2 ). Given the potential threat to self or others, it is absolutely critical that people going through stimulant withdrawal receive the support and treatment they need.

Contact your doctor or seek medical attention right away if you or someone you know is experiencing withdrawal symptoms – especially depression or low mood – after stopping phentermine.

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  1. Hendricks, E. J., Srisurapanont, M., Schmidt, S. L., Haggard, M., Souter, S., Mitchell, C. L., … Greenway F.L. (2014). Addiction potential of phentermine prescribed during long-term treatment of obesity. [Abstract]. International Journal of Obesity, 38(2), 292-298. doi:10.1038/ijo.2013.74
  2. Center for Substance Abuse Treatment. (1999). Chapter 5 – Medical Aspects of Stimulant Use Disorders. In Treatment Improvement Protocol (TIP) (Ser. 33).